69 valiant charging problem

It is not clear to me whether you are driving the 69 or the 73

1970 was the first year for the new style REGULATOR. To use that on a 69 car you must add one new wire and make minor changes to the wiring, AND you must have a 70 or later alternator, which has what is properly called an "isolated field." It has TWO insulated brush connections

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You can use a 1970 alternator with a 69 regulator by grounding either of the two brushes, then hook it up as it was originally.

Some info:

http://www.mymopar.com/index.php?pid=18